This invention concerns a composition for increasing the yield of soybeans. It has significance for agriculture and serves, particularly, for increasing the grain yield of soybeans. The composition according to the present invention can be used with different types of soybean and different times of sowing.
With grain legumes in general, and, particularly, with soybeans, only 30-40% of the induced flowers develop into ripe fruit. On account of the correspondingly high rate of abscission of flowers and unripe fruit, the grain yield is decreased.
With the aim of obtaining an increased yield with grain legumes, and, particularly, with soybeans, various synthetic and natural growth regulators have been examined (Stutte and Davis 1984, Plant Growth Regulating Chemicals (Edit. L.G.Nickell), Vol. 2, pp. 99-112, CRC Press, Boca Raton, Fla.). To these growth regulators belongs also GA.sub.3, which showed yield increasing properties in different soybean cultivars (Abou-Khadrah et al. 1985, 12th International Conference of Plant Growth Substances, Abstracts p. 12, 25 Heidelberg; Dathe et al. 1986, Biochem. Physiol. Pflanzen 181, 615-621; Stutte and Davis 1984). In some cultivars GA.sub.3 caused simultaneously an enhanced shoot growth (cf. Dathe et al. 1986), which results sometimes in a reduction of the shoot stability and may favor the lodging especially in tall cultivars. Thus, the application of GA.sub.3 to soybeans was till now limited to small or semi-tall varieties or to tall varieties less sensitive to GA.sub.3 in growth stimulation.
In contrast to gibberellic acid, salicylic acid alone is not suitable as an active substance in compositions for increasing the yield of soybeans.